1. Field of the Invention
The present invention relates to a battery fault detection apparatus used to monitor a battery pack including battery cells connected in series.
2. Description of Related Art
There are proposed various structures to monitor battery cells for industrial use. For example, Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2002-521792 discloses a structure to monitor the whole of industrial-use batteries by a battery centralized monitoring system constituted of a plurality of cell monitoring devices connected in a daisy chain.
In this structure, the battery centralized monitoring system outputs a command to perform fault diagnosis to the cell monitoring devices in sequence, and diagnosis results by the cell monitoring devices are successively returned to the battery centralized monitoring system.
Each of the cell monitoring devices may be provided with a fault diagnosing function to detect, for example, wire breakage, and a monitoring function to detect overcharge of the cells. In this case, to enable both these two functions, two types of clock signals may be supplied to the cell monitoring devices in a daisy chain manner, the cell monitoring devices being activated by one type of the clock signal, and being changed between the fault diagnosis state and the overcharge detection state by the other type of the clock signal.
However, the above structure has a problem in that it is not possible to determine whether the monitoring state change between the fault diagnosis state and the overcharge detection state has been performed correctly on the side of the cell monitoring devices. Accordingly, if the monitoring state change has not been performed correctly, an erroneous determination on wire breakage or overcharge of the cells may be made.